Author Topic: Chuck backplate with 1" 8tpi thread? (Read 15692 times)

edward · « **on:** March 11, 2015, 06:28:15 AM »

I am in the process of refurbing my Drummond B.S lathe. One thing it is lacking is a 4-jaw chuck. I have a couple of 4-jaws with either no or incorrect backplates.

So I am after a suitable backplate - the nose thread is 1" 8tpi, which appears to be non-standard but the machine I suspect does have a bit of a bastard history as I dont't think the headstock I have matched the bed for a start! I have measured it several times as the thread seems at odds with what the 'usual sources' say it should be, and I am pretty certain it is 8tpi.

The faceplate it came with is a steel disk with a 1"8 nut welded to the back - not too keen on that as a soultion for the backplate!:)

I would prefer a pre-machined thread if at all possible, although I guess I could buy a blank and a suitable tap - although I am not convinced winding in that big a tap is a good idea. Any idea where I might purchase a suitable article?

John Stevenson · « **Reply #1 on:** March 11, 2015, 07:49:42 AM »

Early Myford, ML1 TO ML4 were 1" x 8 tpi to the best of my knowledge, as was the ML8 wood working lathe

vtsteam · « **Reply #2 on:** March 11, 2015, 09:01:12 AM »

Atlas and Sears 6" metal lathes used it -- I believe my Atlas Horizontal mill did also. It's a common size for wood lathe spindles, and you can easily find new wood lathe faceplates here that might be converted to backplates. Taps, too. Also the occasional chuck for above metal lathes. Check Ebay for "1x8 tpi".

vtsteam · « **Reply #3 on:** March 11, 2015, 09:08:07 AM »

Here's one, but not local to you:

http://www.shars.com/products/view/20324/_4_18_Threaded_Back_Plates

edward · « **Reply #4 on:** March 11, 2015, 10:23:49 AM »

nothing is ever simple....

The wood lathe and early myfords were apparently 1"12tpi. Having just spoken to tony at lathes.co.uk, looks like I may have a re-made spindle here.

Hmmm....

edward · « **Reply #5 on:** March 11, 2015, 10:45:32 AM »

Axminster stock a suitable thread backplate for a now obsolete wood lathe chuck. Got one on the way now, hopefully it will fit but if not I can return it. The Drummond may yet rise again!

BaronJ · « **Reply #6 on:** March 11, 2015, 01:12:08 PM »

Quote from: John Stevenson on March 11, 2015, 07:49:42 AM

Early Myford, ML1 TO ML4 were 1" x 8 tpi to the best of my knowledge, as was the ML8 wood working lathe

I believe my ML8 wood lathe is 1" X 12 tpi. Though I must admit never checked it.

edward · « **Reply #7 on:** March 11, 2015, 01:35:32 PM »

Quote from: Baron on March 11, 2015, 01:12:08 PM

Quote from: John Stevenson on March 11, 2015, 07:49:42 AM
Early Myford, ML1 TO ML4 were 1" x 8 tpi to the best of my knowledge, as was the ML8 wood working lathe

I believe my ML8 wood lathe is 1" X 12 tpi. Though I must admit never checked it.

Consensus seems to be the thread should be 1" 12 on this mark of lathe, along with the M type and early Myfords and the ML8 wood lathe. I have spoken to RDG and Myford and they all have backplates like that, but not 8tpi. Apparently there are wood lathes out there with 8tpi noses, and thankfully Axminster have a plate that might fit for their now obsolete 'precision' wood lathe chuck which I might be able to adapt.

If not then time for a bespoke plate, but that is slightly complicated to do on the actual lathe.

I think that the spindle may have been changed at some point. Another little thing sent to try me.

Oh well, onwards and upwards!

edward · « **Reply #8 on:** March 12, 2015, 12:02:12 PM »

time to bang head against wall! The axminster plate is UNC and my nose is Whitworth. It will go on nearly two turns then locks up. Poo.

Time for a re-think.

edward · « **Reply #9 on:** March 12, 2015, 12:13:49 PM »

need to check if this is an insane idea. If I were to run a whitworth tap through the UNC thread would that re-cut the 60° angle to 55°? They are both 8tpi and It should be taking material away.

Or is this mad and there is some awful disaster I am missing? I am probably going to need atap anyway

Sid_Vicious · « **Reply #10 on:** March 12, 2015, 01:43:33 PM »

Isn't the 60< wider than the 55< at the root of the tread?

BaronJ · « **Reply #11 on:** March 12, 2015, 04:30:05 PM »

Quote from: edward on March 12, 2015, 12:13:49 PM

need to check if this is an insane idea. If I were to run a whitworth tap through the UNC thread would that re-cut the 60° angle to 55°? They are both 8tpi and It should be taking material away.

Or is this mad and there is some awful disaster I am missing? I am probably going to need atap anyway

Hi Edward,

1st I can confirm my Myford ML8 wood lathe is 1" X 12 tpi. I checked today.

As far as running a Wit tap through the UNC threads, yes it will recut the thread angle, but you will end up with a sloppy fit !

Now if you have the right Wit tap,why not get hold of a suitable piece of plate, drill it and tap it. Make sure that you can spin it on the spindle, then turn it down to the size you want for your chuck.

edward · « **Reply #12 on:** March 12, 2015, 04:41:58 PM »

I think in all honesty I will go ahead and get a tap, and have a go at making a backplate from scratch. What could possibly go wrong? :-)

BaronJ · « **Reply #13 on:** March 12, 2015, 05:08:09 PM »

Hi Edward,

If you think about what you are doing and don't just jump in with both feet, you won't have a problem. I can't remember if my Drummond lathe had a reference collar behind the threads like my current Myford ML7. But if it does then you will need to make sure that the plate you use is thick enough to have a suitable matching mating surface machined into it.

Some one will moan, but if you can get hold of an old cast iron barbell weight, the ones that are about 1.3" inches thick and are intended for use on a 7/8th" inch bar, you have the perfect starting point. I get things like this from my local scrapyard for pennies (OK a couple of quid) but they are ideal for this job. I made a 5" back plate for my lathe from one. I've also made a tapping stand from a 10" diameter one.

When you come to machine one of these cast iron weights, remember to take your first cut deep enough to get under the very hard skin, even with a carbide tool, otherwise it will simply destroy the cutting edge of the tool. Ten thou would be a good starting point.

Good luck. Take a photo of the work and post it. You know what they say.

AlanT · « **Reply #14 on:** March 13, 2015, 04:48:58 AM »

You can easily run a tap through the Axminster plate and it will work fine afterwards.

A chuck plate has a "register" which does the alignment. The thread just pulls it on.

petertheterrible · « **Reply #15 on:** March 13, 2015, 10:53:03 AM »

What Baron said about using a barbell weight is great advice. Get one that is similar in size to your chuck. All thread on type chucks will have some sort of register that keeps things aligned.

When cutting cast iron on small machines like the ml7, I first use a burr to remove the skin, a lot less hassle than chipping a carbide insert. Externally I use a grinder and remove the scale by hand away from the lathe, less mess better machining.

petertheterrible · « **Reply #16 on:** March 13, 2015, 10:58:24 AM »

This one is made from a castor used on trolleys to hang beef carcasses on. Bought about 100 of these trolleys and have found many uses for these wheels,and trolleys/cages themselves. Threads are single pointed for a myford ml7. Just one way of doing it.

Meldonmech · « **Reply #17 on:** March 13, 2015, 11:18:13 AM »

Edward is your lathe capable of screw cutting? If so doubleboost has made a very good video of how to cut internal and external threads on the lathe. I believe they were 8tpi. I have made several screwed back plates for various lathes in the past, and if you havn't screw cut on a lathe before you could practice on scrap.

Good luck
Cheers David

edward · « **Reply #18 on:** March 13, 2015, 11:35:22 AM »

Loads of great advice, thank you all so much.

I have several options to consider. 'Best' of these is probably to keep a look out for some suitable material and make one. There appear to be commercially available blanks so might even give one of those a whirl if I cant find a barbel or trolley wheel! Thread wise I should really learn to screwcut but it has always terrified me a bit, even watching Johns videos where he does take away some of the fear....

I have ordered a tap as well, just because I can really!

Before any of this happens I need to get the headstock aligned with the bed properly. That isnt going to be much fun but needs must!

petertheterrible · « **Reply #19 on:** March 13, 2015, 11:55:54 AM »

Best advice I could give for a first time threader is to do it by hand. Forget the back gear, remove the drive belt from the motor, if you have a crank, use it otherwise set up the thread pitch you want and use the large reduction pulley to turn. Pretty easy cutting threads even if you don't have adequate kit.

Beginners tend to be overwhelmed by theory, it's good to know theory, but it's better to have a working lathe. Theory is usually not understandable without seeing it practiced first.

Do it by hand, KISS, know your thread angle and pitch, and keep a sharpie handy to mark the increments that you cut with each pass and most importantly, for me at least know the max thread depth and OD or ID.

No motor, no

, preferably wife driven instead.

petertheterrible · « **Reply #20 on:** March 13, 2015, 11:59:50 AM »

And if you made one, keep the threads clean, not like mine. Even if you have perfect threads and alignment it doesn't help if they are dirty.

BaronJ · « **Reply #21 on:** March 15, 2015, 07:00:05 AM »

Quote from: petertheterrible on March 13, 2015, 11:59:50 AM

And if you made one, keep the threads clean, not like mine. Even if you have perfect threads and alignment it doesn't help if they are dirty.

I couldn't agree more.

I've heard some gruesome stories about lathe chucks that screw on nicely but won't unscrew because of detritus hiding in the threads. I made a tool out of a length of 3/16 stainless wire that has two loops in it with short legs at 90 degrees. I filed the ends so that they fitted into the threads of the backplate. The springiness keeps the ends located in the threads whilst turning the tool. Its surprising how much muck lodges in those threads. A toothbrush helps as well. I open the jaws and use the tool by unscrewing it towards the jaws. Be very careful you don't scratch the register though.

Meldonmech · « **Reply #22 on:** March 15, 2015, 11:09:35 AM »

Baron
Like the idea of your springy thread cleaner.

Good tip

Cheers David

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Author Topic: Chuck backplate with 1" 8tpi thread? (Read 15692 times)